用C++写一个带窗口的进度条项目

在C++中创建一个简单的带窗口的进度条项目通常会涉及到Windows API或者一些跨平台的图形库，比如Qt或wxWidgets。这里我会给出一个基本的使用Windows API的例子，展示如何创建一个简单的GUI程序，其中包括一个进度条。

#include <windows.h>
#include <iostream>

// 进度条结构体
struct ProgressBar {
    HWND hWnd; // 窗口句柄
    HINSTANCE hInstance; // 应用实例
    int minValue, maxValue; // 进度条范围
    int value; // 当前进度值
};

void DrawProgressBar(HWND hWnd, ProgressBar& progressBar) {
    // 计算进度条尺寸
    RECT rect;
    GetClientRect(hWnd, &rect);
    int width = rect.right - rect.left;

    // 绘制进度条
    HDC hdc = BeginPaint(hWnd, &PAINTSTRUCT);
    HBRUSH brush = CreateSolidBrush(progressBar.value ? RGB(0, 255, 0) : RGB(255, 0, 0));
    HPEN pen = CreatePen(PS_SOLID, 1, RGB(0, 0, 0));

    // 创建矩形区域
    MoveToEx(hdc, 0, height / 2, NULL);
    LineTo(hdc, width, height / 2);

    // 绘制进度部分
    HGDIOBJ oldPen = SelectObject(hdc, pen);
    DrawRect(hdc, rect.left, rect.top, rect.right * progressBar.value / (progressBar.maxValue - progressBar.minValue), rect.bottom);

    // 绘制完成区域
    SelectObject(hdc, brush);
    FillRect(hdc, &rect, brush);

    // 清理资源
    DeleteObject(brush);
    DeleteObject(pen);
    SelectObject(hdc, oldPen);
    EndPaint(hWnd, &PAINTSTRUCT);
}

LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam) {
    switch (msg) {
        case WM_CREATE:
            // 初始化进度条
            ProgressBar progressBar;
            progressBar.hWnd = hWnd;
            progressBar.hInstance = GetWindowLong(hWnd, GWL_HINSTANCE);
            progressBar.minValue = 0;
            progressBar.maxValue = 100;
            progressBar.value = 0;
            return DefWindowProc(hWnd, msg, wParam, lParam);

        case WM_PAINT:
            DrawProgressBar(hWnd, progressBar);
            break;

        case WM_COMMAND:
            if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL)
                PostQuitMessage(0); // 结束应用
            break;

        default:
            return DefWindowProc(hWnd, msg, wParam, lParam);
    }
    return 0;
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
    WNDCLASS wc = {0};
    wc.lpfnWndProc = WndProc;
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.lpszClassName = "ProgressWindowClass";

    if (!RegisterClass(&wc)) {
        std::cerr << "Failed to register window class!" << std::endl;
        return 0;
    }

    HWND hWnd = CreateWindowEx(NULL,
                               "ProgressWindowClass",
                               "Simple Progress Bar Example",
                               WS_OVERLAPPEDWINDOW,
                               CW_USEDEFAULT, CW_USEDEFAULT,
                               400, 100,
                               NULL, NULL,
                               hInstance, NULL);

    if (!hWnd) {
        std::cerr << "Failed to create window!" << std::endl;
        return 0;
    }

    MSG msg;
    while (GetMessage(&msg, NULL, 0, 0)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return 0;
}